Investigators are working to determine the cause of a fiery crash that killed "Fast & Furious" star Paul Walker and his driver-friend as fans gathered at the crash site to erect a makeshift memorial in honor of the actor.

The crash also killed Walker's friend, professional driver Roger Rodas, according to Walker's publicist, Ame Van Iden. She said Walker was a passenger in the car when they drove away from a fundraiser in the community of Valencia Saturday. The two bodies were so badly burned that officials said they would use dental records to make a postive identification.

Walker, 40, and Rodas, 38, had thrown a fundraiser benefiting victims of the recent typhoon in the Philippines. The event was held by Reach Out Worldwide, a charity Walker founded in 2010 to aid victims of natural disasters.

The crash happened in a business park just a few blocks away from the charity event. The Porsche smashed into a light pole and tree. Sheriff's deputies found the car engulfed in flames when they arrived. Witnesses tried to put the fire out, but both men were pronounced dead at the scene.

Jim Torp was at the charity event and spoke to both men just before they rode off.

"'Hey, I'll be right back in 5 minutes.' Those are the last words I heard," Torp told ABC News.

Police tell ABC News the impact of the crash was so great, a chunk of the car flew several feet into a nearby building, breaking a window.

Walker has been on break from filming "Fast & Furious 7," the latest installment in the "Fast & Furious" franchise which has been one of the most successful in recent memory. Universal Pictures has not said what it plans to do with "Fast & Furious 7," which was slated for release in July.

"The real question is how long they are going to take to figure out the direction of the film and to make everyone comfortable with coming back to work," Hollywood Reporter executive editor Matthew Belloni said.

Walker had recently finished work on "Brick Mansions," which was in post-production. Another film, "Hours," a drama about Hurricane Katrina and its aftermath, was due to be released Dec. 13.

Walker is survived by his 15-year-old daughter, Meadow. The actor was never married.